1) Purchase a grannie square blanket from Goodwill.2) Plop in washing machine, fill with hot water, wash. If the blanket changed texture it is feltable and therefor mostly wool.3) Repeat washing process until desired texture is reached.4) Slice the grannie square rows up into individual long strips.5) Trim the joining yarn on the sides very close to the edge of the grannie squares. Pick off excess joining yarn.

Thanks! I was so stoked when I got it out of the washing machine and found that it had felted! So hopefully most of those grannie blankets out there are wool!I guess it would work without the felting, but I feel a lot more confident cutting into it when it's felted. More sturdy, and the crochet won't unravel even if you do make a mistake cutting.